Patent GB-1058390-A (GB)
Title: Polyimides and a process for their preparation
IPC: C09D5/25
Filed: 1964-10-28
Abstract: A tetracarboxylic acid diester of formula <FORM:1058390/C2/1> where R12 is alkyl or aralkyl and the 4 carbonyl groups attached to A are in pairs, each pair comprising an ester and an acid carbonyl group and being attached to adjacent carbon atoms in A, may be produced by reacting the corresponding tetracarboxylic acid dianhydride and mono-functional alcohol.  Dianhydrides specified include benzophenone - 3,31,4,41 - tetracarboxylic acid dianhydride and pyromellitic acid dianhydride. Alcohols specified include methanol, ethanol and butanol.  The reaction may take place in a solvent.  Solvents specified include dimethyl acetamide and N-methyl-pyrrolidone. A nitrogen atmosphere may be used.ALSO:A polyimide is prepared from a diamine of formula NH2-M-NH2 and a diester of a tetracarboxylic acid of formula <FORM:1058390/C3/1> where M and A are organic, R12 is alkyl or where M and A are organic, R12 is alkyl or aralkyl and the 4 carbonyl groups are in pairs, each of a pair being attached to adjacent carbon atoms, at least one out of the diamine and diester containing a ketone group and being present in at least 30 molar per cent, the diamine being present in at least 15 molar per cent of the diester.  The ketone groups give rise to cross-links of structure >C = N-M-N = C<, at least 20 per cent of the units being cross linked, A may be aliphatic, alicyclic, aromatic or heterocyclic and may optionally be substituted by F, Cl, Br, NO2, COOH, or COOZ where Z alkyl, alkaryl, aryl or aralkyl.  Amines specified include: bis-(4-aminophenyl) ether, bis-(4-aminophenyl) methane, bis-(aminocyclohexyl) methane, nonamethylene diamine, benzophenone - 4,41 - diamine, hexamethylene diamines, pyridine derivatives and sulphur, phosphorus and silicon containing compounds. The diester may be prepared from the corresponding tetracarboxylic acid or its dianhydride and an alcohol, e.g. methanol, ethanol, propanol, butanol and benzyl alcohol, in a solvent.  Many solvents are specified. Diester-specified include: esters of benzophenones 3,314,41-tetra-carboxylic acid, pyromellitic acid, pheaylmethane tetracarboxylic acid diphenyl ether tetracarboxylic acid, tetracarboxylic acids of condensed aromatic systems and of secondary and tertiary nitrogen, sulphur, phosphorus and silicon containing groupings. The reactants may be mixed dry or in a solvent, e.g. dimethyl acetamide or N-methyl pyrrolidone.  More than one example of both or either reactant may be present.  Up to 50 mole per cent of a reactive monomer may be present. Other additives may be reactive polymers, pigments, dyes, inorganic and organic fillers. Additives specified include Al, Al2, O3, xylene, Zn, metal oxides and salts, epoxy-resins, epoxy novolacs, polyphenylene oxides, aminoplast resins, polyamides, polyesters, and addition polymers having reactive pendant groups. The reactants may be heated at 80-150 DEG  C. until all the solvent is removed and then at 150-500 DEG  C.  The product may be used as an adhesive, wire enamel, varnish, supported or unsupported film or a laminate.  The adhesive compositions may contain heat stabilizers, e.g. arsenic thioarsenate, copper-8-quinolinolate, arsenic pentoxide, an iron chelate, or an organophosphorus compound.ALSO:Adhesive compositions based on polyimides (see Division C3) may be applied to woven or non-woven glass fabrics, metal screens, refrasil fabrics, graphite cloth, asbestos cloth, papers, films and cloth-like fabrics of high melting synthetic polymers such as wholly aromatic polyamides and polytetrafluoroethylene.  Fillers such as aluminium dust, powdered asbestos, aluminium oxide powder, iron powder, flake glass, tin dust, zinc dust, zinc tetraoxychromate and chromic oxide may be present as well as other resins such as phenolic resins, epoxide resins, silicone resins, nitrogen resins and polyesters.  Suitable resins are listed.  Heat stabilizers such as organo-metallic compounds, may be present and are listed.  The glass fabrics may be cleaned with chromyl chloride or by heating before application of the compositions which may be cured at 50 - 200 DEG C. after coating.  As substrates may be aluminium alloys, stainless steel, cold rolled steel, magnesium, titanium, copper, brass, galvanized iron, glass, ceramic, silicone resins, phenolic resins and polytetrafluoroethylene.  A doctor blade may be used and coatings applied to copper wire, glass rings and glass and aluminium panels.  Overcoat layers such as of epoxy resins, silicone resins, novolac and resole resins, polyvinyl formal acetol or butyral resins, polyurethanes, alkyds, polyamide resins, polyester resins, aminoplast resns and polytetrafluoroethylene may be applied.